21229290 has 40 divisors (see below), whose sum is σ = 57085380. Its totient is φ = 5660928.

The previous prime is 21229261. The next prime is 21229297. The reversal of 21229290 is 9292212.

It can be written as a sum of positive squares in 2 ways, for example, as 20820969 + 408321 = 4563^2 + 639^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21229297) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 12295 + ... + 13914.

Almost surely, 2^21229290 is an apocalyptic number.

21229290 is an abundant number, since it is smaller than the sum of its proper divisors (35856090).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21229290 is a wasteful number, since it uses less digits than its factorization.

21229290 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26228 (or 26219 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 21229290 is about 4607.5253661809. The cubic root of 21229290 is about 276.8929021609.

The spelling of 21229290 in words is "twenty-one million, two hundred twenty-nine thousand, two hundred ninety".